Found in old American documentation, this circuit is current as it uses the 555 to modulate an infrared LED. Pulses are set by R1.
To use the instrument for AC measurement, the tips are A and B. For CC use tips A or B for...
The interesting circuit shown in the figure, can have its gain digitally controlled and present two...
This simple MW radio was found in a 1975 publication, but it can be mounted with BC548...